OK, I just tried that again, and it won't let me intall the 5.1 version. The install button is just greyed out now.

Crash analyzer says

This crash was caused when trying to draw or interact with a user interface element. A common cause for this crash is a corrupt or outdated version of the ProKit or BrowserKit frameworks, but in some cases it may be a DVD Studio Pro bug that should be reported to Apple. Users sometimes get this error if they upgrade their OS without reinstalling Final Cut Studio or if their HIToolbox preferences are corrupt.

When trying to open DVDSP. Tomorrow I have to help someone create a 13 language, 7 segment DVD with 13 forced subtitles, so it's been great timing lol.